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The thermodynamic model of inorganic arsenic species in aqueous solutions Potentiometric study of the hydrolitic equilibrium of arsenic acid.

Authors :
Raposo JC
Sanz J
Zuloaga O
Olazabal MA
Madariaga JM
Source :
Talanta [Talanta] 2002 Jul 03; Vol. 57 (5), pp. 849-57.
Publication Year :
2002

Abstract

Protonation constants of arsenic acid were determined at different ionic strengths in NaClO(4) (0.1, 0.5, 1.0, 3.0 mol dm(-3)), NaCl (0.5 and 1.0 mol dm(-3)) and KCl (0.5, 1.0 and 3.0 mol dm(-3)) ionic media by means of a potentiometric study. The distribution of arsenate species was defined depending on two important variables in natural environments: pH and composition. All the experimentation was performed at 25 degrees C. The differences found in the protonation constants for different medium compositions, were explained by the different behaviour of the interaction parameters of the species considered in the different media and ionic strengths. These parameters were reported for all hydrolitic As(V) species and were calculated using the Modified Bromley's Methodology (MBM). The corresponding thermodynamic stepwise formation constants were also determined (log degrees K(1)=11.58+/-0.01, log degrees K(2)=7.06+/-0.01, log degrees K(3)=2.25+/-0.01). All the results obtained showed not only the importance of the ionic strength but also of the composition of the ionic medium on the distribution of the acid-base species of As(V) as a function of pH in natural waters.

Details

Language :
English
ISSN :
1873-3573
Volume :
57
Issue :
5
Database :
MEDLINE
Journal :
Talanta
Publication Type :
Academic Journal
Accession number :
18968688
Full Text :
https://doi.org/10.1016/s0039-9140(02)00130-3